I'm using HTML tables to create a timetable. Each row represents half hour, and the cells can span multiple rows by using
Row [N] of a row group established by aelement has no cells
beginning on it.
You can’t have empty rows in a table in a valid HTML document per the current HTML spec.
Maybe you rightly should be able to, but the spec currently clearly says that you can’t. So if anybody believes it should be allowed by the spec, the right thing to do is to file an issue against the HTML Standard in its github tracker or even write a patch and open a PR for it.
Specifically the spec defines the following error case:
If there exists a row or column in the table containing only slots that do not have a cell anchored to them, then this is a table model error.
In Internet-spec terms, that is a “normative” authoritative statement that can’t be ignored or overridden by anything else. It is stating a hard requirement.
The spec elsewhere says this:
trelement: Content model
https://html.spec.whatwg.org/multipage/tables.html#the-tr-element Zero or more td, th, and script-supporting elements
But that’s not actually a contradiction and does not conflict with or supersede or override the “table model error” requirement cited above. In fact, it’s the opposite—the “table model error” requirement supersedes the more-liberal requirement in the other section (cited above) that a valid
tr element can have zero or more children.
Any stricter requirements in a spec always supersede or override any more-liberal requirements.